The component with the lowest price in the CYLINDER HEAD COVER schematic is the Dowel,pin,14x20.
On this parts fiche the Bolt,flange12x150 is the most specified component.
Parts such as the Cylinder Head Cover: Holder,rocker Arm, Rubber, Mount, Bolt,spl.6x45,5, Cover,cyln Head are included in the Cx500 1980 (a) European Direct Sales Cylinder Head Cover parts fiche.